Method for integrated substrate processing in copper metallization

ABSTRACT

A method of copper metallization includes providing a patterned substrate containing a via and a trench, and performing an integrated process on the patterned substrate. The integrated process includes depositing a first metal-containing layer over the patterned substrate, removing by sputter etching the first metal-containing layer from the bottom of the via and at least partially removing the first metal-containing layer from the bottom of the trench, depositing a conformal Ru layer onto the sputter etched first metal-containing layer, depositing a Cu alloying metal layer onto the conformal Ru layer, and plating Cu over the patterned substrate. According to one embodiment, the method can further include depositing a second metal-containing layer onto the sputter etched first metal-containing layer prior to depositing the conformal Ru layer. According to another embodiment, a Cu alloying metal may be deposited onto the plated Cu and the plated Cu annealed.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is related to U.S. patent application Ser. No.11/277,908, entitled METHOD FOR INTEGRATING A CONFORMAL RUTHENIUM LAYERINTO COPPER METALLIZATION OF HIGH ASPECT RATIO FEATURES, the entirecontent of which is herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to semiconductor processing andsemiconductor devices, and more particularly, to a method of integratinga conformal ruthenium (Ru) layer into copper metallization used insemiconductor devices.

BACKGROUND OF THE INVENTION

An integrated circuit contains various semiconductor devices and aplurality of conducting metal paths that provide electrical power to thesemiconductor devices and allow these semiconductor devices to share andexchange information. Within the integrated circuit, metal layers arestacked on top of one another using intermetal or interlayer dielectriclayers that insulate the metal layers from each other.

Normally, each metal layer must form an electrical contact to at leastone additional metal layer. Such electrical contact is achieved byetching a hole (i.e., a via) in the interlayer dielectric that separatesthe metal layers, and filling the resulting via with a metal to createan interconnect. Metal layers typically occupy etched pathways in theinterlayer dielectric. A “via” normally refers to any feature such as ahole, line or other similar feature formed within a dielectric layerthat provides an electrical connection through the dielectric layer to aconductive layer underlying the dielectric layer. Similarly, metallayers connecting two or more vias are normally referred to as trenches.

The use of copper (Cu) metal in multilayer metallization schemes formanufacturing integrated circuits creates problems due to high mobilityof Cu atoms in dielectrics, such as SiO₂, and Cu atoms may createelectrical defects in Si. Thus, Cu metal layers, Cu filled trenches, andCu filled vias are normally encapsulated with a barrier material toprevent Cu atoms from diffusing into the dielectrics and Si. Barrierlayers are normally deposited on trench and via sidewalls and bottomsprior to Cu seed deposition, and may include materials that arepreferably non-reactive and immiscible in Cu, provide good adhesion tothe dielectrics and can offer low electrical resistivity.

An increase in device performance is normally accompanied by a decreasein device area or an increase in device density. An increase in devicedensity requires a decrease in via dimensions used to forminterconnects, including a larger aspect ratio (i.e., depth to widthratio). As via dimensions decrease, and aspect ratios increase, itbecomes increasingly more challenging to form diffusion barrier layerswith adequate thickness on the sidewalls of the vias. In addition, asvia and trench dimensions decrease and the thicknesses of the layers inthe vias and trenches decrease, the material properties of the layersand the layer interfaces become increasingly more important. Inparticular, the processes forming those layers need to be carefullyintegrated into a manufacturable process sequence where good control ismaintained for all the steps of the process sequence.

SUMMARY OF THE INVENTION

Embodiments of the invention provide a method for integrated substrateprocessing in Cu metallization. The method integrates a conformal Rulayer into Cu metallization of high aspect ratio features.

According to one embodiment of the invention, the method includesproviding a patterned substrate containing a via having a sidewall and abottom and a trench having a sidewall and a bottom, and performing anintegrated process on the patterned substrate. The integrated processincludes depositing a first metal-containing layer over the patternedsubstrate, removing the first metal-containing layer substantiallycompletely from the bottom of the via and at least partially from thebottom of the trench by sputter etching to leave a sputter etched firstmetal-containing layer on a portion of the patterned substrate,depositing a conformal Ru layer onto the sputter etched firstmetal-containing layer, depositing a Cu alloying metal layer over theconformal Ru layer, and plating Cu over the Cu alloying metal layer.According to another embodiment, prior to depositing the conformal Rulayer, a second metal-containing layer may be deposited onto the sputteretched first metal-containing layer. According to still anotherembodiment, the first metal-containing layer may be substantiallycompletely removed from the bottom of the via and from the bottom of thetrench by sputter etching, and a second metal-containing layer depositedonto the sputter etched layer prior to depositing the conformal Rulayer.

According to one embodiment of the invention, the method includesproviding a patterned substrate containing a via having a sidewall and abottom and a trench having a sidewall and a bottom, and performing anintegrated process on the patterned substrate. The integrated processincludes depositing a first metal-containing layer over the patternedsubstrate, removing the first metal-containing layer substantiallycompletely from the bottom of the via and at least partially from thebottom of the trench by sputter etching to leave a sputter etched firstmetal containing layer on a portion of the patterned substrate,depositing a conformal Ru layer over the first metal-containing layerincluding onto the sputter etched first metal-containing layer,depositing a Cu layer onto the conformal Ru layer, plating Cu over theCu layer, depositing a Cu alloying metal layer over the plated Cu, andannealing the plated Cu. According to another embodiment, prior todepositing the conformal Ru layer, a second metal-containing layer maybe deposited onto the sputter etched first metal-containing layer.According to still another embodiment, the first metal-containing layermay be substantially completely removed from the bottom of the via andfrom the bottom of the trench by sputter etching, and a secondmetal-containing layer deposited onto the sputter etched firstmetal-containing layer prior to depositing the conformal Ru layer.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will become readily apparent with reference to thefollowing detailed description, particularly when considered inconjunction with the accompanying drawings, in which:

FIG. 1 depicts a schematic view of a vacuum processing tool forprocessing a patterned substrate according to embodiments of theinvention;

FIG. 2 depicts a schematic view of a thermal chemical vapor deposition(TCVD) system for depositing a Ru adhesion layer according to anembodiment of the invention;

FIG. 3 depicts a schematic view of a TCVD system for depositing a Ruadhesion layer according to another embodiment of the invention;

FIGS. 4A-4G show schematic cross-sectional views of the formation of adual damascene patterned substrate containing a conformal Ru layerintegrated with copper metallization according to an embodiment of theinvention;

FIG. 5 is a process flow diagram for processing a patterned substrateaccording to an embodiment of the invention;

FIGS. 6A-6F show schematic cross-sectional views of the formation of adual damascene patterned substrate containing a conformal Ru layerintegrated with copper metallization according to an embodiment of theinvention; and

FIG. 7 is a process flow diagram for processing a patterned substrateaccording to an embodiment of the invention.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS OF THE INVENTION

In the following description, in order to facilitate a thoroughunderstanding of the invention and for purposes of explanation and notlimitation, specific details are set forth, such as a particulargeometry of processing systems and a vacuum processing tool anddescriptions of various components. However, it should be understoodthat the invention may be practiced in other embodiments that departfrom these specific details.

Embodiments of the invention provide a system and method for integratinga conformal Ru layer into copper metallization of a semiconductor devicecontaining a patterned substrate with high aspect ratio features. Thedual damascene patterned substrate contains a trench and a via formed inthe patterned substrate, where the trench and the via contain sidewallsand bottoms. The via can have an aspect ratio (depth/width) greater thanor equal to about 1:1, for example 2:1, 3:1, 4:1, 5:1, 6:1, 12:1, 15:1,or higher. The via can have widths of about 200 nm or less, for example150 nm, 100 nm, 65 nm, 32 nm, 20 nm, or lower. However, embodiments ofthe invention are not limited to these aspect ratios or via widths, asother aspect ratios or via widths may be utilized. Often, aspect ratiosof at least 5:1 are referred to as “high” aspect ratios.

According to one embodiment of the invention, the method includesproviding a patterned substrate, where the patterned substrate containsa via and a trench, and performing an integrated process on thepatterned substrate. In particular, a first metal-containing layer isdeposited onto the patterned substrate and, thereafter, the firstmetal-containing layer is substantially completely removed by sputteretching from the bottom of the via and at least partially removed fromthe bottom of the trench. Removal of the first metal-containing layerfrom the bottom of the via provides low electrical resistance to a metallayer at the bottom of the via and bulk copper to be deposited over thepatterned substrate. Next, a conformal Ru layer is deposited. In anexemplary embodiment, the Ru layer is deposited in a thermal chemicalvapor deposition process using a process gas containing Ru₃(CO)₁₂ vaporand CO gas.

Thereafter, a Cu alloying metal layer is deposited over the conformal Rulayer. A thickness of the Cu alloying metal layer can, for example, bebetween about 1 nm and about 50 nm, or greater. The Cu alloying metallayer can include metal that forms an alloy with Cu metal and improvesthe material properties of the Cu metallization formed over thepatterned substrate. The improved material properties can includestronger adhesion between Cu and the Ru layer, and improved stress- andelectro-migration of the Cu. According to embodiments of the invention,the Cu alloying metal layer can include Cu and transition metals ornon-transition metals such as alkali metals or alkali earth metals.Examples of alloying metals include, but are not limited to, Mg, Mn, Mo,Al, Cr, Ti, Nb, Ca, Be, Zn, Cd, Ag, Pd, or Au, or a combination of twoor more thereof. In one example, a layer of Al may be utilized as the Cualloying metal layer.

Following deposition of the layer of a Cu alloying metal layer, Cumetallization is formed over the patterned substrate, filling both thevia and trench with bulk Cu. In one embodiment, the patterned substrateis exposed to air and the feature (via and trench) filled with bulk Cuby a Cu plating process, such as an electroless plating process or anelectrolytical plating process, and planarized (e.g., by chemicalmechanical polishing (CMP)).

A patterned substrate processed according to embodiments of theinvention contains a conformal Ru layer that provides conformal coverageover high aspect ratio features, and provides, in combination with oneor more underlying metal-containing layers, good diffusion barrierproperties, good adhesion to bulk Cu layer filling the high aspect ratiofeatures, and good stress-migration and electro-migration properties.

Embodiments of the invention provide integration of different “unit”processes under well-controlled processing conditions. Unit processescan include processes for depositing different material layers on asubstrate. Such unit processes are frequently performed in differentprocessing systems where the patterned substrate (wafer) may be exposedto air as it is transported from one processing system to the next.According to an embodiment of the invention, unit processes that includedeposition of a first metal-containing layer, sputter etching of thefirst metal-containing layer, deposition of a second metal-containinglayer, deposition of a conformal Ru layer, deposition of a Cu alloyingmetal layer, and deposition of a non-conformal Cu layer, are performedin sequence without air exposure in a vacuum processing tool, therebyavoiding air exposure that may be detrimental to the different materiallayers deposited by the unit processes and improving the properties ofthe interfaces between the different material layers.

FIG. 1 depicts a schematic view of a vacuum processing tool forprocessing a patterned substrate according to embodiments of theinvention. The vacuum processing tool 300 contains substrate loadingchambers 310 and 320, processing systems 330-360, robotic transfersystem 370, and controller 380. According to an embodiment of theinvention, the vacuum processing tool 300 allows for processing thepatterned substrate without exposure to air during the processing.

The substrate loading chambers 310 and 320 are utilized for transferringpatterned substrates into the vacuum processing tool 300 for processingand out of the vacuum processing tool 300 following processing. Sincethe vacuum processing tool 300 is normally under vacuum, the substrateloading chambers 310 and 320 are configured to evacuate substratesdisposed into the vacuum processing tool 300. As shown in FIG. 1, thesubstrate loading chambers 310 and 320 are coupled to the robotictransfer system 370. The robotic transfer system 370 is configured fortransferring substrates between the substrate loading chambers 310 and320 and the processing systems 330-360. The robotic transfer system 370can, for example, be purged with an inert gas such as Ar under vacuumconditions (e.g., about 100 mTorr or less).

According to an embodiment of the invention, the processing system 330can be configured for depositing a first metal-containing layer, such asa Ta-containing layer (e.g., TaC, TaN, TaCN), a Ti-containing layer(e.g., Ti, TiN), or a W-containing layer (e.g., W, WN). In addition, theprocessing system 330 may be configured for depositing a secondmetal-containing layer, such as a Ta, Ti, TiN, TaC, TaCN, W, or WN.According to another embodiment, the second metal-containing layer maybe deposited by another processing system (not shown) coupled throughvacuum to the vacuum processing tool 300. The processing system 340 canbe configured for depositing a conformal Ru layer by a chemical vapordeposition process, the processing system 350 can be configured fordepositing a Cu alloying metal, and the processing system 360 can beconfigured for depositing a Cu layer.

Although not shown in FIG. 1, those skilled in the art will readilyrealize that the vacuum processing tool 300 may also contain a degassingsystem and a pre-clean system. Degassing may be carried out followingevacuation when the patterned substrate is disposed in the vacuumprocessing tool 300. The degassing can, for example, be performed byheating the substrate to a temperature between about 100° C. and about500° C. in the presence of an inert gas such as Ar. Pre-cleaning mayinclude light plasma cleaning of the patterned substrate. Furthermore,the vacuum processing tool 300 may also contain a cool-down systemconfigured for cooling a processed substrate, and a substrate aligningsystem.

Following degassing and/or pre-cleaning, the patterned substrate istransported by the robotic transfer system 370 to the processing system330 for depositing a first metal-containing layer. According to oneembodiment of the invention, the processing system 330 can be configuredto carry out physical vapor deposition (PVD) of a Ta-containing layer(e.g., TaC, TaN, TaCN), a Ti-containing layer (e.g., Ti, TiN), or aW-containing layer (e.g., W, WN). In one example, the firstmetal-containing layer can be deposited from a sputtering target using anitrogen-containing gas (e.g., NH₃ or N₂) in a plasma. In anotherexample, the processing system 330 can be configured to carry outionized physical vapor deposition (IPVD) of the first metal-containinglayer. One example of an IPVD system is described in U.S. Pat. No.6,287,435. In yet another example, the processing system 330 can beconfigured to deposit the first metal-containing layer byplasma-enhanced chemical vapor deposition (PECVD) or by aplasma-enhanced atomic layer deposition (PEALD) process (e.g., usingalternating steps of adsorbing a metal-containing precursor on a surfaceof a substrate and exposing the adsorbed metal-containing precursor to areducing plasma). One example of a PEALD processing system is describedin U.S. Patent Application Publication No. 2006/0211246 A1. According toone embodiment of the invention, the processing system 330 can beconfigured for depositing a TaCN first metal-containing layer by a PEALDprocess that includes alternating exposures of TAIMATA andplasma-excited hydrogen. In still another example, the processing system330 can be configured to carry out thermal chemical vapor deposition(TCVD) or ALD of the first metal-containing layer.

According to one embodiment of the invention, the processing system 330can be further configured for sputter etching the deposited firstmetal-containing layer to remove the first metal-containing layer fromthe bottom of a via and to at least partially remove the firstmetal-containing layer from the bottom of a trench. According to anotherembodiment of the invention, sputter etching of the first metalcontaining layer may be omitted from the process.

Following deposition (and sputter etching of the first metal-containinglayer), a second metal-containing layer may be deposited by theprocessing system 330 or by another processing system (not shown)coupled through vacuum to the vacuum processing tool 300. The secondmetal-containing layer may be a Ta layer, a Ti layer, or a W layerdeposited by PVD or IPVD. According to another embodiment of theinvention, a TaCN second metal-containing layer may be deposited by aPEALD process. According to still another embodiment of the invention, asecond metal-containing layer may be deposited by thermal chemical vapordeposition (TCVD) or ALD. According to yet another embodiment of theinvention, deposition of the second metal-containing layer may beomitted.

Next, the substrate is transported by the robotic transfer system 370 tothe processing system 340 for depositing a conformal Ru layer, forexample, in a thermal chemical vapor deposition process using a processgas containing Ru₃(CO)₁₂ and CO. The processing system 340 can, forexample, be one of the deposition systems 1, 100 depicted in FIGS. 2, 3,as discussed below.

Following deposition of the conformal Ru layer in the processing system340, the patterned substrate may be transported by the robotic transfersystem 370 to the processing system 350 to deposit a Cu alloying metalon the conformal Ru layer. The processing system 350 may be configuredto deposit the layer of alloying metal by PVD, IPVD, PEALD, TCVD, orALD.

Next, the patterned substrate may be transported to the processingsystem 360 to deposit a Cu layer on the layer of Cu alloying metal. TheCu layer can have a thickness between 1 and 50 nm. The processing system360 can, for example, be an IPVD system configured for depositing the Culayer. According to one embodiment of the invention, the processingsystem 360 can be configured for sputter etching the firstmetal-containing layer.

A plating system 390 is operatively coupled to the vacuum processingtool 300 through the substrate loading chamber 310. The plating system390 can, for example, be configured for performing an electrochemical orelectroless plating process for plating a bulk Cu layer. Electrochemicaland electroless plating systems are well known to those skilled in theart and are readily available commercially. Normally, the vacuumprocessing tool 300 is configured to expose the substrate to air duringtransfer from the substrate loading chamber 310 to plating system 390.

The vacuum processing tool 300 can be controlled by a controller 380.The controller 380 can be coupled to and exchange information withsubstrate loading chambers 310 and 320, processing systems 330-360, androbotic transfer system 370. The controller 380 can operate substratetransfer operations within the vacuum processing tool 300 and substrateprocessing performed within the processing systems 330-360. In oneexample, the controller 380 can further control the plating system 390.In another example, the plating system 390 can contain a separatecontroller for controlling the functions of the plating system 390. Inone embodiment of the invention, the controller 380 can be programmedthrough a program stored in the memory of the controller 380 to performprocesses of embodiments of the invention and any functions associatedwith monitoring the processes. The controller 380 may be a systemscontroller, a dedicated hardware circuit, or a programmed generalpurpose computer, such as a DELL PRECISION WORKSTATION 610™, availablefrom Dell Corporation, Austin, Tex.

FIG. 2 depicts a schematic view of a thermal chemical vapor deposition(TCVD) system for depositing a Ru adhesion layer from a Ru₃(CO)₁₂precursor according to an embodiment of the invention. It should beunderstood, however, that Ru precursors other than Ru₃(CO)₁₂ may be usedin embodiments of the present invention. The deposition system 1includes a process chamber 10 having a substrate holder 20 configured tosupport a substrate 25 upon which the ruthenium metal layer is formed.The process chamber 10 is coupled to a metal precursor vaporizationsystem 50 via a vapor precursor delivery system 40.

The process chamber 10 is further coupled to a vacuum pumping system 38through a duct 36, wherein the pumping system 38 is configured toevacuate the process chamber 10, vapor precursor delivery system 40, andmetal precursor vaporization system 50 to a pressure suitable forforming the conformal Ru metal layer on the substrate 25, and suitablefor vaporization of the Ru₃(CO)₁₂ precursor 52 in the metal precursorvaporization system 50.

Still referring to FIG. 2, the metal precursor vaporization system 50 isconfigured to store a Ru₃(CO)₁₂ precursor 52, to heat the Ru₃(CO)₁₂precursor 52 to a temperature sufficient for vaporizing the Ru₃(CO)₁₂precursor 52, and to introduce Ru₃(CO)₁₂ precursor vapor to the vaporprecursor delivery system 40. The Ru₃(CO)₁₂ precursor 52 is a solidunder the selected heating conditions in the metal precursorvaporization system 50. In order to achieve the desired temperature forsubliming the solid Ru₃(CO)₁₂ precursor 52, the metal precursorvaporization system 50 is coupled to a vaporization temperature controlsystem 54 configured to control the vaporization temperature. Forinstance, the temperature of the Ru₃(CO)₁₂ precursor 52 is generallyelevated to approximately 40° C. to approximately 45° C. in conventionalsystems in order to sublime the Ru₃(CO)₁₂. At this temperature, thevapor pressure of the Ru₃(CO)₁₂, for instance, ranges from approximately1 to approximately 3 mtorr. As the Ru₃(CO)₁₂ precursor 52 is heated tocause sublimation, a CO-containing gas can be passed over or through theRu₃(CO)₁₂ precursor 52, or a combination thereof. The CO-containing gascontains CO and optionally an inert carrier gas, such as N₂, or a noblegas (i.e., He, Ne, Ar, Kr, or Xe), or a combination thereof. In oneexample, the metal precursor vaporization system 50 may be a multi-trayvaporization system configured for efficient evaporation and transportof the Ru₃(CO)₁₂ vapor. An exemplary multi-tray vaporization system isdescribed in U.S. Patent Application Publication No. 2006/0112882 A1.

For example, a gas supply system 60 is coupled to the metal precursorvaporization system 50, and it is configured to, for instance, supplyCO, a carrier gas, or a mixture thereof, beneath the Ru₃(CO)₁₂ precursor52 via feed line 61, or over the Ru₃(CO)₁₂ precursor 52 via feed line62. This setup allows for flowing the CO gas in contact with the solidRu₃(CO)₁₂ precursor in the metal precursor vaporization system 50 tocapture Ru₃(CO)₁₂ precursor vapor in the CO gas as the vapor is beingformed. In addition, or in the alternative, the gas supply system 60 iscoupled to the vapor precursor delivery system 40 downstream from themetal precursor vaporization system 50 to supply the gas to the vapor ofthe Ru₃(CO)₁₂ precursor 52 via feed line 63 as or after it enters thevapor precursor delivery system 40. Although not shown, the gas supplysystem 60 can comprise a carrier gas source, a CO gas source, one ormore control valves, one or more filters, and a mass flow controller.For instance, the flow rate of the CO-containing gas can be betweenabout 0.1 standard cubic centimeters per minute (sccm) and about 1000sccm. Alternately, the flow rate of the CO-containing gas can be betweenabout 10 sccm and about 500 sccm. Still alternately, the flow rate ofthe CO-containing gas can be between about 50 sccm and about 200 sccm.According to embodiments of the invention, the flow rate of theCO-containing gas can range from approximately 0.1 sccm to approximately1000 sccm. Alternately, the flow rate of the CO-containing gas can bebetween about 1 sccm and about 500 sccm.

Downstream from the metal precursor vaporization system 50, the processgas containing the Ru₃(CO)₁₂ precursor vapor flows through the vaporprecursor delivery system 40 until it enters the process chamber 10 viaa vapor distribution system 30 coupled thereto. The vapor precursordelivery system 40 can be coupled to a vapor line temperature controlsystem 42 in order to control the vapor line temperature and preventdecomposition of the Ru₃(CO)₁₂ precursor vapor as well as condensationof the Ru₃(CO)₁₂ precursor vapor. The vapor precursor delivery system 40can, for example, be maintained at a temperature between 50° C. and 100°C.

Referring again to FIG. 2, the vapor distribution system 30, which formspart of and is coupled to the process chamber 10, comprises a vapordistribution plenum 32 within which the vapor disperses prior to passingthrough a vapor distribution plate 34 and entering a processing zone 33above substrate 25. In addition, the vapor distribution plate 34 can becoupled to a distribution plate temperature control system 35 configuredto control the temperature of the vapor distribution plate 34.

Once the process gas containing the Ru₃(CO)₁₂ precursor vapor enters theprocessing zone 33 of process chamber 10, the Ru₃(CO)₁₂ precursor vaporthermally decomposes upon adsorption at the substrate surface due to theelevated temperature of the substrate 25, and a conformal Ru metal layeris formed on the substrate 25. The substrate holder 20 is configured toelevate the temperature of the substrate 25 by virtue of the substrateholder 20 being coupled to a substrate temperature control system 22.For example, the substrate temperature control system 22 can beconfigured to elevate the temperature of the substrate 25 up toapproximately 500° C. Additionally, the process chamber 10 can becoupled to a chamber temperature control system 12 configured to controlthe temperature of the chamber walls.

Metal precursor vaporization systems utilized for providing Ru₃(CO)₁₂vapor have contemplated operating within a temperature range ofapproximately 40° C. to approximately 45° C. for Ru₃(CO)₁₂ under vacuumconditions in order to prevent decomposition, which occurs at highertemperatures. For example, Ru₃(CO)₁₂ can decompose at elevatedtemperatures to form by-products, such as those illustrated below:Ru₃(CO)₁₂(ad)

Ru₃(CO)_(x)(ad)+(12−x)CO(g)   (1)or,Ru₃(CO)_(x)(ad)

3Ru(s)+xCO(g)   (2)wherein these by-products can adsorb (ad), i.e., condense, on theinterior surfaces of the deposition system 1. The accumulation ofmaterial on these surfaces can cause problems from one substrate to thenext, such as process repeatability. Alternatively, for example,Ru₃(CO)₁₂ can condense on the internal surfaces of the deposition system1, viz.Ru₃(CO)₁₂(g)

Ru₃(CO)₁₂(ad)  (3).

In summary, the low vapor pressure of Ru₃(CO)₁₂ precursors and the smallprocess window result in a very low deposition rate of a Ru metal layeron the substrate 25.

Vaporizing the Ru₃(CO)₁₂ precursor in the presence of CO gas can reducethe above-mentioned problems that limit the delivery of the Ru₃(CO)₁₂precursor to the substrate. Thus, according to an embodiment of theinvention, the CO gas is added to the Ru₃(CO)₁₂ precursor vapor byflowing the CO gas through or over the solid Ru₃(CO)₁₂ precursor in themetal precursor vaporization system 50 to reduce dissociation of theRu₃(CO)₁₂ precursor vapor, thereby shifting the equilibrium in Equation(1) to the left and reducing premature decomposition of the Ru₃(CO)₁₂precursor in the vapor precursor delivery system 40 prior to delivery ofthe Ru₃(CO)₁₂ precursor to the process chamber 10. It has been shownthat addition of the CO gas to the Ru₃(CO)₁₂ precursor vapor allows forincreasing the vaporization temperature from approximately 40° C. toapproximately 100° C., or higher. The elevated temperature increases thevapor pressure of the Ru₃(CO)₁₂ precursor, resulting in increaseddelivery of the Ru₃(CO)₁₂ precursor to the process chamber and, hence,increased deposition rate of the Ru metal on the substrate 25.Furthermore, it has been visually observed that flowing a mixture of Arand the CO gas over or through the Ru₃(CO)₁₂ precursor reduces prematuredecomposition of the Ru₃(CO)₁₂ precursor.

According to an embodiment of the invention, the addition of CO gas to aRu₃(CO)₁₂ precursor vapor allows for maintaining the Ru₃(CO)₁₂ precursorvaporization temperature from approximately 40° C. to approximately 150°C. Alternately, the vaporization temperature can be maintained atapproximately 60° C. to approximately 90° C.

Since the addition of the CO gas to the Ru₃(CO)₁₂ precursor vaporincreases the thermal stability of the Ru₃(CO)₁₂ precursor vapor, therelative concentration of the Ru₃(CO)₁₂ precursor vapor to the CO gas inthe process gas can be utilized to control the decomposition rate of theRu₃(CO)₁₂ precursor on the substrate 25 at a certain substratetemperature. Furthermore, the substrate temperature can be utilized tocontrol the decomposition rate (and thereby the deposition rate) of theRu metal on the substrate 25. As those skilled in the art will readilyappreciate, the amount of CO gas and the substrate temperature caneasily be varied to allow for a desired vaporization temperature of theRu₃(CO)₁₂ precursor and for achieving a desired deposition rate of theRu₃(CO)₁₂ precursor on the substrate 25.

Furthermore, the amount of CO gas in the process gas can be selected sothat Ru metal deposition on the substrate 25 from a Ru₃(CO)₁₂ precursoroccurs in a kinetic-limited temperature regime (also commonly referredto as a reaction rate limited temperature regime). For example, theamount of CO gas in the process gas can be increased until the Ru metaldeposition process is observed to occur in a kinetic-limited temperatureregime. A kinetic-limited temperature regime refers to the range ofdeposition conditions where the deposition rate of a chemical vapordeposition process is limited by the kinetics of the chemical reactionsat the substrate surface, typically characterized by a strong dependenceof deposition rate on temperature. Unlike the kinetic-limitedtemperature regime, a mass-transfer limited regime is normally observedat higher substrate temperatures and includes a range of depositionconditions where the deposition rate is limited by the flux of chemicalreactants to the substrate surface. A mass-transfer limited regime ischaracterized by a strong dependence of deposition rate on Ru₃(CO)₁₂precursor flow rate and is independent of deposition temperature. Metaldeposition in the kinetic-limited regime normally results in good stepcoverage and good conformality (uniform thickness) of the metal layer onpatterned substrates.

Still referring to FIG. 2, the deposition system 1 can further include acontrol system 80 configured to operate and control the operation of thedeposition system 1. The control system 80 is coupled to the processchamber 10, the substrate holder 20, the substrate temperature controlsystem 22, the chamber temperature control system 12, the vapordistribution system 30, the vapor precursor delivery system 40, themetal precursor vaporization system 50, and the gas supply system 60.

FIG. 3 depicts a schematic view of a TCVD system for depositing a Ruadhesion layer with a Ru₃(CO)₁₂ precursor according to anotherembodiment of the invention. The deposition system 100 comprises aprocess chamber 110 having a substrate holder 120 configured to supporta substrate 125 upon which the conformal Ru metal layer is formed. Theprocess chamber 110 is coupled to a precursor delivery system 105 havingmetal precursor vaporization system 150 configured to store and vaporizea Ru₃(CO)₁₂ precursor 152, and a vapor precursor delivery system 140configured to transport the vapor of the Ru₃(CO)₁₂ precursor 152 to theprocess chamber 110.

The process chamber 110 comprises an upper chamber section 111, a lowerchamber section 112, and an exhaust chamber 113. An opening 114 isformed within lower chamber section 112, where lower chamber section 112couples with exhaust chamber 113.

Still referring to FIG. 3, substrate holder 120 provides a horizontalsurface to support substrate (or wafer) 125, which is to be processed.The substrate holder 120 can be supported by a cylindrical supportmember 122, which extends upward from the lower portion of exhaustchamber 113. Furthermore, the substrate holder 120 comprises a heater126 coupled to substrate holder temperature control system 128. Theheater 126 can, for example, include one or more resistive heatingelements. Alternately, the heater 126 can, for example, include aradiant heating system, such as a tungsten-halogen lamp. The substrateholder temperature control system 128 can include a power source forproviding power to the one or more heating elements, one or moretemperature sensors for measuring the substrate temperature or thesubstrate holder temperature, or both, and a controller configured toperform at least one of monitoring, adjusting, or controlling thetemperature of the substrate 125 or substrate holder 120.

During processing, the heated substrate 125 can thermally decompose theRu₃(CO)₁₂ precursor vapor, and enable deposition of a Ru metal layer onthe substrate 125. The substrate holder 120 is heated to apre-determined temperature that is suitable for depositing the desiredRu metal layer onto the substrate 125. Additionally, a heater (notshown) coupled to a chamber temperature control system 121 can beembedded in the walls of process chamber 110 to heat the chamber wallsto a pre-determined temperature. The heater can maintain the temperatureof the walls of process chamber 110 from about 40° C. to about 150° C.,or from about 40° C. to about 80° C. A pressure gauge (not shown) isused to measure the process chamber pressure. According to an embodimentof the invention, the process chamber pressure can be between about 1mtorr and about 200 mtorr. Alternately, the process chamber pressure canbe between about 2 mtorr and about 50 mtorr.

Also shown in FIG. 3, a vapor distribution system 130 is coupled to theupper chamber section 111 of process chamber 110. Vapor distributionsystem 130 comprises a vapor distribution plate 131 configured tointroduce precursor vapor from vapor distribution plenum 132 to aprocessing zone 133 above substrate 125 through one or more orifices134.

Furthermore, an opening 135 is provided in the upper chamber section 111for introducing a Ru₃(CO)₁₂ precursor vapor from vapor precursordelivery system 140 into vapor distribution plenum 132. Moreover,temperature control elements 136, such as concentric fluid channelsconfigured to flow a cooled or heated fluid, are provided forcontrolling the temperature of the vapor distribution system 130, andthereby prevent the decomposition or condensation of the Ru₃(CO)₁₂precursor inside the vapor distribution system 130. For instance, afluid, such as water, can be supplied to the fluid channels from a vapordistribution temperature control system 138. The vapor distributiontemperature control system 138 can include a fluid source, a heatexchanger, one or more temperature sensors for measuring the fluidtemperature or vapor distribution plate temperature or both, and acontroller configured to control the temperature of the vapordistribution plate 131 from about 20° C. to about 150° C. For aRu₃(CO)₁₂ precursor, the temperature of the vapor distribution plate 131can be maintained at or above a temperature of about 65° C. to avoidprecursor condensation on the plate 131.

As illustrated in FIG. 3, a metal precursor vaporization system 150 isconfigured to hold a Ru₃(CO)₁₂ precursor 152 and to evaporate (orsublime) the Ru₃(CO)₁₂ precursor 152 by elevating the temperature of theRu₃(CO)₁₂ precursor. The terms “vaporization,” “sublimation” and“evaporation” are used interchangeably herein to refer to the generalformation of a vapor (gas) from a solid or liquid precursor, regardlessof whether the transformation is, for example, from solid to liquid togas, solid to gas, or liquid to gas. A precursor heater 154 is providedfor heating the Ru₃(CO)₁₂ precursor 152 to maintain the Ru₃(CO)₁₂precursor 152 at a temperature that produces a desired vapor pressure ofRu₃(CO)₁₂ precursor 152. The precursor heater 154 is coupled to avaporization temperature control system 156 configured to control thetemperature of the Ru₃(CO)₁₂ precursor 152. For example, the precursorheater 154 can be configured to adjust the temperature of the Ru₃(CO)₁₂precursor 152 from about 40° C. to about 150° C., or from about 60° C.to about 90° C.

As the Ru₃(CO)₁₂ precursor 152 is heated to cause evaporation (orsublimation), a CO-containing gas can be passed over or through theRu₃(CO)₁₂ precursor 152, or combination thereof. The CO-containing gascontains CO and optionally an inert carrier gas, such as N₂, or a noblegas (i.e., He, Ne, Ar, Kr, Xe). According to an embodiment of theinvention, a CO gas can be added to the inert gas. Alternately, otherembodiments contemplate the CO gas replacing the inert gas. For example,a gas supply system 160 is coupled to the metal precursor vaporizationsystem 150, and it is configured to, for instance, flow the CO gas, theinert gas, or both, over or through the Ru₃(CO)₁₂ precursor 152.Although not shown in FIG. 3, gas supply system 160 can also oralternatively be coupled to the vapor precursor delivery system 140 tosupply the carrier gas and/or CO gas to the vapor of the Ru₃(CO)₁₂precursor 152 as or after it enters the vapor precursor delivery system140. The gas supply system 160 can comprise a gas source 161 containingan inert carrier gas, a CO gas, or a mixture thereof, one or morecontrol valves 162, one or more filters 164, and a mass flow controller165. For instance, the mass flow rate of the CO-containing gas can rangefrom approximately 0.1 sccm to approximately 1000 sccm.

Additionally, a sensor 166 is provided for measuring the total gas flowfrom the metal precursor vaporization system 150. The sensor 166 can,for example, comprise a mass flow controller, and the amount ofRu₃(CO)₁₂ precursor vapor delivered to the process chamber 110 can bedetermined using sensor 166 and mass flow controller 165. Alternately,the sensor 166 can comprise a light absorption sensor to measure theconcentration of the Ru₃(CO)₁₂ precursor in the gas flow to the processchamber 110.

A bypass line 167 can be located downstream from sensor 166, and it canconnect the vapor precursor delivery system 140 to an exhaust line 116.Bypass line 167 is provided for evacuating the vapor precursor deliverysystem 140, and for stabilizing the supply of the Ru₃(CO)₁₂ precursorvapor to the process chamber 110. In addition, a bypass valve 168,located downstream from the branching of the vapor precursor deliverysystem 140, is provided on bypass line 167.

Referring still to FIG. 3, the vapor precursor delivery system 140comprises a high conductance vapor line having first and second valves141 and 142, respectively. Additionally, the vapor precursor deliverysystem 140 can further comprise a vapor line temperature control system143 configured to heat the vapor precursor delivery system 140 viaheaters (not shown). The temperatures of the vapor lines can becontrolled to avoid condensation of the Ru₃(CO)₁₂ precursor vapor in thevapor line. The temperature of the vapor lines can be controlled fromabout 20° C. to about 100° C., or from about 40° C. to about 90° C.

Moreover, a CO gas can be supplied from a gas supply system 190. Forexample, the gas supply system 190 is coupled to the vapor precursordelivery system 140, and it is configured to, for instance, mix the COgas with the Ru₃(CO)₁₂ precursor vapor in the vapor precursor deliverysystem 140, for example, downstream of valve 141. The gas supply system190 can comprise a CO gas source 191, one or more control valves 192,one or more filters 194, and a mass flow controller 195. For instance,the mass flow rate of CO gas can range from approximately 0.1 sccm toapproximately 1000 sccm.

Mass flow controllers 165 and 195, and valves 162, 192, 168, 141, and142 are controlled by controller 196, which controls the supply,shutoff, and the flow of the inert carrier gas, the CO gas, and theRu₃(CO)₁₂ precursor vapor. Sensor 166 is also connected to controller196 and, based on output of the sensor 166, controller 196 can controlthe carrier gas flow through mass flow controller 165 to obtain thedesired Ru₃(CO)₁₂ precursor flow to the process chamber 110.

As illustrated in FIG. 3, the exhaust line 116 connects exhaust chamber113 to pumping system 118. A vacuum pump 119 is used to evacuate processchamber 110 to the desired degree of vacuum, and to remove gaseousspecies from the process chamber 110 during processing. An automaticpressure controller (APC) 115 and a trap 117 can be used in series withthe vacuum pump 119. The vacuum pump 119 can include a turbo-molecularpump (TMP) capable of a pumping speed up to 500 liters per second (andgreater). Alternately, the vacuum pump 119 can include a dry roughingpump. During processing, the process gas can be introduced into theprocess chamber 110, and the chamber pressure can be adjusted by the APC115. The APC 115 can comprise a butterfly-type valve or a gate valve.The trap 117 can collect unreacted Ru₃(CO)₁₂ precursor material andby-products from the process chamber 110.

Referring back to the substrate holder 120 in the process chamber 110,as shown in FIG. 3, three substrate lift pins 127 (only two are shown)are provided for holding, raising, and lowering the substrate 125. Thesubstrate lift pins 127 are coupled to plate 123, and can be lowered tobelow the upper surface of substrate holder 120. A drive mechanism 129utilizing, for example, an air cylinder provides means for raising andlowering the plate 123. Substrate 125 can be transferred into and out ofprocess chamber 110 through gate valve 200 and chamber feed-throughpassage 202 via a robotic transfer system (not shown), and received bythe substrate lift pins 127. Once the substrate 125 is received from thetransfer system, it can be lowered to the upper surface of the substrateholder 120 by lowering the substrate lift pins 127.

Still referring to FIG. 3, a controller 180 includes a microprocessor, amemory, and a digital I/O port capable of generating control voltagessufficient to communicate and activate inputs of the deposition system100 as well as monitor outputs from the deposition system 100. Moreover,the controller 180 is coupled to and exchanges information with processchamber 110; precursor delivery system 105, which includes controller196, vapor line temperature control system 143, and vaporizationtemperature control system 156; vapor distribution temperature controlsystem 138; vacuum pumping system 118; and substrate holder temperaturecontrol system 128. In the vacuum pumping system 11 8, the controller180 is coupled to and exchanges information with the APC 115 forcontrolling the pressure in the process chamber 110. A program stored inthe memory is utilized to control the aforementioned components ofdeposition system 100 according to a stored process recipe. One exampleof a controller 180 is a DELL PRECISION WORKSTATION 610™, available fromDell Corporation, Dallas, Tex.

The controller 180 may be implemented as a general purpose computersystem that performs a portion or all of the microprocessor-basedprocessing steps of the invention in response to a processor executingone or more sequences of one or more instructions contained in a memory.Such instructions may be read into the controller memory from anothercomputer readable medium, such as a hard disk or a removable mediadrive. One or more processors in a multi-processing arrangement may alsobe employed as the controller microprocessor to execute the sequences ofinstructions contained in main memory. In alternative embodiments,hard-wired circuitry may be used in place of or in combination withsoftware instructions. Thus, embodiments are not limited to any specificcombination of hardware circuitry and software.

The controller 180 includes at least one computer readable medium ormemory, such as the controller memory, for holding instructionsprogrammed according to the teachings of the invention and forcontaining data structures, tables, records, or other data that may benecessary to implement the present invention. Examples of computerreadable media are compact discs, hard disks, floppy disks, tape,magneto-optical disks, PROMs (EPROM, EEPROM, flash EPROM), DRAM, SRAM,SDRAM, or any other magnetic medium, compact discs (e.g., CD-ROM), orany other optical medium, punch cards, paper tape, or other physicalmedium with patterns of holes, a carrier wave (described below), or anyother medium from which a computer can read.

Stored on any one or on a combination of computer readable media, thepresent invention includes software for controlling the controller 1 80,for driving a device or devices for implementing the invention, and/orfor enabling the controller to interact with a human user. Such softwaremay include, but is not limited to, device drivers, operating systems,development tools, and applications software. Such computer readablemedia further includes the computer program product of the presentinvention for performing all or a portion (if processing is distributed)of the processing performed in implementing the invention.

The computer code devices of the present invention may be anyinterpretable or executable code mechanism, including but not limited toscripts, interpretable programs, dynamic link libraries (DLLs), Javaclasses, and complete executable programs. Moreover, parts of theprocessing of the present invention may be distributed for betterperformance, reliability, and/or cost.

The term “computer readable medium” as used herein refers to any mediumthat participates in providing instructions to the processor of thecontroller 180 for execution. A computer readable medium may take manyforms, including but not limited to, non-volatile media, volatile media,and transmission media. Non-volatile media includes, for example,optical disks, magnetic disks, and magneto-optical disks, such as thehard disk or the removable media drive. Volatile media includes dynamicmemory, such as the main memory. Moreover, various forms of computerreadable media may be involved in carrying out one or more sequences ofone or more instructions to the processor of the controller forexecution. For example, the instructions may initially be carried on amagnetic disk of a remote computer. The remote computer can load theinstructions for implementing all or a portion of the present inventionremotely into a dynamic memory and send the instructions over a networkto the controller 180.

The controller 180 may be locally located relative to the depositionsystem 100, or it may be remotely located relative to the depositionsystem 100. For example, the controller 180 may exchange data with thedeposition system 100 using at least one of a direct connection, anintranet, the Internet or a wireless connection. The controller 180 maybe coupled to an intranet at, for example, a customer site (i.e., adevice maker, etc.), or it may be coupled to an intranet at, forexample, a vendor site (i.e., an equipment manufacturer). Additionally,for example, the controller 180 may be coupled to the Internet.Furthermore, another computer (i.e., controller, server, etc.) mayaccess, for example, the controller 180 to exchange data via at leastone of a direct connection, an intranet, and the Internet. As also wouldbe appreciated by those skilled in the art, the controller 180 mayexchange data with the deposition system 100 via a wireless connection.

Reference will now be made to FIGS. 4A-4G, FIG. 5, and FIG. 1. FIGS.4A-4G show schematic cross-sectional views of the formation of a dualdamascene patterned substrate containing a conformal Ru layer integratedwith Cu metallization according to an embodiment of the invention. FIG.5 is a process flow diagram for processing a patterned substrateaccording to an embodiment of the invention.

The process 500 of the process flow diagram shown in FIG. 5 may beperformed using the vacuum processing tool 300 depicted in FIG. 1. Instep 502, a patterned substrate 400 depicted in FIG. 4A containing a via426 and a trench 424 is provided in the vacuum processing tool 300. Thepatterned substrate 400 can, for example, be loaded into the substrateloading chamber 320 and the substrate loading chamber 320 evacuated. Theexemplary patterned substrate 400 depicted in FIG. 4A includes a dualdamascene pattern containing a first metallization layer 412 (e.g., Cu),a dielectric (insulating layer) 414 (e.g., SiO₂, a low-k dielectricmaterial such as fluorinated silicon glass (FSG), carbon doped oxide, apolymer, or any other suitable dielectric material), a trench etch stoplayer 416 (e.g., SiN), a trench level dielectric 418 (e.g., SiO₂), a viaetch stop 420 (e.g., SiN), a via level dielectric 422 (e.g., SiO₂), atrench 424 having a sidewall 424 a and bottom 424 b etched through thetrench level dielectric 418, and a via 426 having a sidewall 426 a andbottom 426 b etched through the via level dielectric 422. The patternedsubstrate 400 can be formed using standard lithography and etchingmethods known to those skilled in the art. It will be understood thatsubstrates with more complicated dual damascene patterns than theexemplary patterned substrate 400 may be employed.

Once evacuated, the patterned substrate 400 may be degassed and/orpre-cleaned as described above in reference to FIG. 1. Next, thepatterned substrate 400 is transferred to the processing system 330 bythe robotic transfer system 370. Once in the processing system 330, instep 504, a first metal-containing layer 428 is deposited over thepatterned substrate 400. As depicted in FIG. 4B, the firstmetal-containing layer 428 conformally covers the “field” 427 (areaaround the trench 424), and the sidewalls (424 a, 426 a) and the bottoms(424 b, 426 b) of the trench 424 and the via 426. However, this is notrequired for the invention, as the first metal-containing layer 428 maybe non-conformal. According to an embodiment of the invention, the firstmetal-containing layer 428 can contain a Ta-containing layer such asTaN, TaC, or TaCN, a Ti-containing layer such as Ti or TiN, or aW-containing layer such as W or WN. The first metal-containing layer 428can, for example, have a thickness between about 0.5 and about 10 nm.

In step 506, the first metal-containing layer 428 is sputter etched toremove, substantially completely the first metal-containing layer 428from the bottom 426 b of the via 426 and from the bottom 424 b of thetrench 424. By “substantially completely” is meant that some particlesor residue may remain, but that a continuous layer does not remain. Inthe embodiment depicted in FIG. 4C, the first metal-containing layer 428is fully removed from the bottom 426 b of the via 426, the bottom 424 bof the trench 424, and the “field” 427 (area around the trench 424) butnot from the sidewall 424 a of the trench 424 and the sidewall 426 a ofthe via 426. This is due to the lower sputter etch rates at thesidewalls. Thus, a sputter etched first metal-containing layer 428 aremains on sidewalls 424 a and 426 a. At the bottom 426 b of the via426, a portion of the first metallization layer 412 may also be removedin area 431 by the sputter etching as depicted in FIG. 4C. According toone embodiment of the invention, the processing system 330 may beconfigured for both depositing the first metal-containing layer 428 instep 504 and performing the sputter etching step 506. The sputteretching can utilize Ar gas where a typical process pressure may includeabout 10 mTorr to about 10 Torr.

The removal of the first metal-containing layer 428 from the bottom 426b of the via 426 in step 506 provides a low electrical resistivity pathbetween the first metallization layer 412 and a second metallizationlayer (i.e., Cu) that will fill the trench 424 and the via 426 (see FIG.4G).

In step 508, a second metal-containing layer 430 may be deposited overthe patterned substrate 400, specifically over sputter etched firstmetal-containing layer 428 a, field 427, trench bottom 424 b and area431, as depicted in FIG. 4D. According to one embodiment of theinvention, the second metal-containing layer can contain Ta, Ti, TiN,TaC, TaCN, W, or WN. The second metal-containing layer 430 can provide ametal-containing growth surface for a conformal Ru layer to be depositedonto the patterned substrate 400. In particular, as depicted in FIG. 4C,the first metal-containing layer 428 was removed from the field 427 andthe bottom 424 b of the trench 424, thereby leaving those areas void ofthe first metal-containing layer 428. In addition, the secondmetal-containing layer 430 may provide a diffusion barrier for moistureout-diffusion from the dielectric materials of the patterned substrate400. According to another embodiment of the invention, step 508 may beomitted.

In step 510, a conformal Ru layer 432 is deposited onto the patternedsubstrate 400. The conformal Ru layer 432 shown in FIG. 4E can bedeposited in a thermal chemical vapor deposition process using a processgas containing Ru₃(CO)₁₂ and CO as described above in reference to FIGS.2 and 3. According to one embodiment of the invention, the substrate canbe maintained at a temperature between 120° C. and about 350° C. duringthe deposition of the conformal Ru layer 432. Alternately, a differentRu deposition technique and/or precursor may be used.

A thin (<5 nm thick) conformal Ru layer has greatly improved diffusionresistance to Cu when, according to the invention, the conformal Rulayer 432 is deposited onto a metal-containing layer, such as the secondmetal-containing layer 430 (or the first metal-containing layer 428),compared to when a thin conformal Ru layer is deposited directly ontodielectric materials. Since the second metal-containing layer 430 isdeposited onto the existing layers on the sidewalls 424 a and 426 a ofthe trench 424 and the via 426, the thickness of the secondmetal-containing layer 430 may be low in those areas compared to thefield 427 and trench bottom 424 b areas containing dielectric surfacesvoid of the first metal-containing layer 428. In one example, theminimum total thickness of the conformal Ru layer 432, the sputteretched first metal-containing layer 428 a, and the secondmetal-containing layer 430 can be between 1 nm and 10 nm. Alternately,the minimum total thickness can be between 1 nm and 5 nm. For example, athickness of the conformal Ru layer 432 can be between 0.5 and 15 nm,for example 1 nm, 2 nm, 3 nm, or 4 nm.

In step 512, a Cu alloying metal layer 434 is deposited onto theconformal Ru layer 432. According to one embodiment of the invention,the Cu alloying metal layer 434 may be formed by depositing a layercontaining a Cu alloying metal, and depositing a Cu metal layer onto theCu alloying metal. According to another embodiment of the invention, theCu alloying metal layer 434 may be formed by depositing a layercontaining a mixture of a Cu alloying metal and a Cu metal. In oneexample, the mixture can be deposited by PVD or IPVD using a sputteringtarget containing the mixture. According to one embodiment, the Cualloying metal can include Mg, Mn, Mo, Al, Cr, Ti, Nb, Ca, Be, Zn, Cd,Ag, Pd, or Au, or a combination of two or more thereof. A thickness ofthe Cu alloying metal layer 434 can be between 1 nm and 50 nm, orgreater.

The Cu alloying metal layer 434 depicted in FIG. 4F is non-conformal butthis is not required for the invention as the layer 434, or one or moresublayers of the layer 434 may be conformally deposited. When used withthe conformal Ru layer 432, the non-conformal Cu alloying metal layer434 may be thinner than a conventional Cu seed layer used for Cu plating(e.g., a Cu seed layer on a Ta layer), where the thickness is commonlygreater than about 50 nm. Importantly, little or no Cu alloying metallayer 434 needs to be deposited inside the trench 424 and the via 426,since subsequent Cu plating may be performed directly onto the Ru layer432 inside the trench 424 and the via 426. Therefore, the non-conformalCu alloying metal layer 434 may have very low step coverage, for exampleless than 10%. The non-conformal Cu alloying metal layer 434 is thick onthe “field”, thereby providing a low-resistivity path for conductingcurrent from the substrate edge to the entire substrate surface. Asthose skilled in the art will readily recognize, the amount of Cualloying metal layer 434 deposited in the bottom 424 b and 426 b areaswill depend on the widths and depths of the trench 424 and the via 426.Furthermore, since scaling of future semiconductor devices will continueto ever smaller minimum feature sizes, trench and via widths willcontinue to decrease and trench and via depths will continue toincrease. Therefore, the amount of the Cu alloying metal layer 434inside the trenches and vias will continue to decrease. However,embodiments of the invention require little or no Cu metal to bedeposited inside the trench 424 and the via 426, thereby providing amethod for successfully performing Cu metallization of the patternedsubstrate 400 for the future scaling of semiconductor devices. A role ofa non-conformal Cu alloying metal layer 434 includes reducing theterminal (‘resistive substrate’) effect that is commonly encountered inelectrochemical plating processing where a non-uniform thickness of theplated Cu layer over the whole substrate (wafer) is observed. Theterminal effect is the tendency for the current density to benon-uniform as a result of the ohmic potential drop associated withconducting current from the substrate edge to the entire substratesurface through a thin resistive layer. This problem can be more severefor a relatively high resistance non-Cu layer (e.g., Ru layer 432) thana lower resistivity Cu layer. The sheet resistance of a non-Cu layer canbe orders of magnitude higher than that of today's Cu seed layers andstraightforward extension of methods currently used to manipulatecurrent distribution (e.g., electrolyte conductivity) generally may notbe adequate to combat the terminal effect experienced using a non-Cuseed layer without the non-conformal Cu alloying metal layer 434.

In step 514, the patterned substrate 400 depicted in FIG. 4F can beexposed to air and subsequently a bulk Cu layer 436 plated onto thepatterned substrate 400 and planarized using chemical mechanicalpolishing (CMP) to yield the patterned substrate 400 shown in FIG. 4G.Although at least a portion of the non-conformal Cu layer may becomeoxidized upon exposure to air, any oxidized Cu may be removed during theplating process. According to an embodiment of the invention, the platedbulk Cu layer 436 may be annealed, for example at a temperature betweenabout 100° C. and about 150° C. for 30 minutes.

According to another embodiment of the invention, the Cu alloying metallayer 434 may be a Cu layer and a Cu alloying metal deposited over theplated Cu. In particular, a Cu layer may be deposited onto the conformalRu layer, Cu plated onto the Cu layer, a layer of Cu alloying metaldeposited over the plated Cu, and the plated Cu annealed.

Reference will now be made to FIGS. 6A-6F, FIG. 7, and FIG. 1. FIGS.6A-6F show schematic cross-sectional views of the formation of a dualdamascene patterned substrate containing a conformal Ru layer integratedwith copper metallization according to another embodiment of theinvention. FIG. 7 is a process flow diagram for processing a patternedsubstrate according to an embodiment of the invention.

The process 700 of the process flow diagram shown in FIG. 7 may beperformed using the vacuum processing tool 300 depicted in FIG. 1. Instep 702, a patterned substrate 600 depicted in FIG. 6A containing a via626 and a trench 624 is provided in the vacuum processing tool 300. Thepatterned substrate 600 can, for example, be loaded into the substrateloading chamber 320 and the substrate loading chamber 320 evacuated. Thepatterned substrate 600 includes a dual damascene pattern containing afirst metallization layer 612 (e.g., Cu), a dielectric (insulatinglayer) 614 (e.g., SiO₂, a low-k dielectric material such as fluorinatedsilicon glass (FSG), carbon doped oxide, a polymer, or any othersuitable dielectric material), a trench etch stop layer 616 (e.g., SiN),a trench level dielectric 618 (e.g., SiO₂), a via etch stop 620 (e.g.,SiN), a via level dielectric 622 (e.g., SiO₂), a trench 624 having asidewall 624 a and bottom 624 b etched through the trench leveldielectric 618, and a via 626 having a sidewall 626 a and bottom 626 betched through the via level dielectric 622.

Once evacuated, the patterned substrate 600 may be degassed and/orpre-cleaned as described above in reference to FIG. 1. Next, thepatterned substrate 600 is transferred to the processing system 330 bythe robotic transfer system 370. Once in the processing system 330, instep 704, a first metal-containing layer 628 is deposited over thepatterned substrate 600. Unlike the first metal-containing layer 428depicted in FIG. 4B that conformally covers the field 427 and thesidewalls (424 a, 426 a) and the bottoms (424 b, 426 b) of the trench424 and the via 426, the first metal-containing layer 628 depicted inFIG. 6B is non-conformal with greater thicknesses in the field 627 andtrench bottom 624 b than on the sidewalls 624 a, 626 a of the trench 624and via 626 and via bottom 626 b. The first metal-containing layer 628may be deposited by a deposition process that can provide non-conformaldeposition, for example, an IPVD process.

In step 706, the patterned substrate 600 is sputter etched to remove thefirst metal-containing layer 628 from the bottom 626 b of the via 626and to partially remove the first metal-containing layer 628 from thebottom 624 b of the trench 624 and the field 627, thereby formingsputter etched layer 628 a that covers the field 627, the entire trench624 and the via sidewall 626 a. At the bottom 626 b of the via 626, aportion of the first metallization layer 612 may be removed in area 631as depicted in FIG. 6C. According to one embodiment of the invention,the processing system 330 may be configured for both depositing thefirst metal-containing layer 628 in step 704 and performing the sputteretching step 706.

Unlike the process flow 500 in FIG. 5, where a second metal-containinglayer 430 was deposited onto the sputter etched patterned substrate 400,the process flow 700 depicted in FIG. 7 includes depositing a conformalRu layer directly onto the sputter etched first metal-containing layer628 a without depositing a second metal-containing layer. Unlike in FIG.4C, where the first metal-containing layer 428 was fully removed fromthe field 427 and trench bottom 424 b areas, the sputter etched firstmetal-containing layer 628 a in FIG. 6C still contains at least aportion of the first metal-containing layer 628 on the bottom 624 b, andthe sidewalls 624 a, 626 a of the trench 624 and via 626, therebyallowing for omitting the deposition of a second metal-containing layer.

Alternately, since the first metal-containing layer 628 is non-conformaland may have poor coverage on the sidewalls 624 a, 626 a of the trench624 and via 626, a second conformal metal-containing layer (not shown)may be deposited before the first metal-containing layer 628, followedby depositing the first metal-containing layer 628 thereon and sputteretching both the first and second metal-containing layers tosubstantially completely remove the layers from the bottom 626 b of thevia 626 and at least partially from the bottom 624 b of the trench 624,and then followed by deposition of the conformal Ru layer 632. Asdescribed above in reference to FIG. 4D, a conformal Ru layer hasgreatly improved diffusion resistance to Cu when the conformal Ru layeris deposited onto a metal-containing layer compared to when the thinconformal Ru layer is deposited directly onto dielectric materials. Inone example, the minimum total thickness of the conformal Ru layer 632and the sputter etched first metal-containing layer 628 a can be between1 nm and 10 nm. Alternately, the minimum total thickness can be between1 nm and 5 nm. For example, a thickness of the conformal Ru layer 632can be between 0.5 and 15 nm, for example 1 nm, 2 nm, 3 nm, or 4 nm.Alternately, according to another embodiment of the invention, a secondmetal-containing layer may be deposited onto the sputter etched firstmetal-containing layer 628 a depicted in FIG. 6C prior to depositing aconformal Ru layer 632.

Once in the processing system 340, in step 708, a conformal Ru layer 632is deposited onto the patterned substrate 600. The conformal Ru layer632 shown in FIG. 6D can be deposited in a thermal chemical vapordeposition process using a process gas containing Ru₃(CO)₁₂ and CO asdescribed above in reference to FIGS. 2 and 3. According to oneembodiment of the invention, the substrate can be maintained at atemperature between 120° C. and about 350° C. during the deposition ofthe conformal Ru layer 632. Alternately, a different Ru depositiontechnique and/or precursor may be used.

Next, once in the processing system 350, in step 710, a Cu alloyingmetal layer 634 is deposited onto the conformal Ru layer 632. Accordingto one embodiment of the invention, the Cu alloying metal layer 634 maybe formed by depositing a layer containing a Cu alloying metal, anddepositing a Cu metal layer onto the Cu alloying metal. According toanother embodiment of the invention, the Cu alloying metal layer 634 maybe formed by depositing a layer containing a mixture of a Cu alloyingmetal and a Cu metal. In one example, the mixture can be deposited byPVD or IPVD using a sputtering target containing the mixture. Accordingto one embodiment, the Cu alloying metal can include Mg, Mn, Mo, Al, Cr,Ti, Nb, Ca, Be, Zn, Cd, Ag, Pd, or Au, or a combination of two or morethereof. A thickness of the Cu alloying metal layer 634 can be between 1nm and 50 nm, or greater.

After performing steps 702-710, the patterned substrate 600 depicted inFIG. 6E can be exposed to air and subsequently, in step 712, a bulk Culayer 636 plated onto the patterned substrate 600 and planarized usingchemical mechanical polishing (CMP) to yield the patterned substrate 600shown in FIG. 6F.

According to another embodiment of the invention, the Cu alloying metallayer 634 may be a Cu layer and a Cu alloying metal deposited over theplated Cu. In particular, a Cu layer may be deposited onto the conformalRu layer, Cu plated onto the Cu layer, a layer of Cu alloying metaldeposited over the plated Cu, and the plated Cu annealed.

Although only certain exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

1. A method of integrated substrate processing, comprising: providing apatterned substrate containing a via having a sidewall and a bottom anda trench having a sidewall and a bottom; performing an integratedprocess on the patterned substrate, the process comprising: depositing afirst metal-containing layer over the patterned substrate; removing thefirst metal-containing layer substantially completely from the bottom ofthe via and at least partially from the bottom of the trench by sputteretching to leave a sputter etched first metal-containing layer on aportion of the patterned substrate; depositing a conformal Ru layer overthe sputter etched first metal-containing layer; depositing a Cualloying metal layer over the conformal Ru layer; and plating Cu overthe Cu alloying metal layer.
 2. The method according to claim 1, whereinthe depositing a first metal-containing layer comprises depositing Ta,TaN, TaC, TaCN, Ti, TiN, W, or WN.
 3. The method according to claim 1,further comprising, prior to depositing the conformal Ru layer,depositing a second metal-containing layer over the sputter etched firstmetal-containing layer.
 4. The method according to claim 3, wherein thedepositing a second metal-containing layer comprises depositing Ta, TaN,TaC, TaCN, Ti, TiN, W, or WN.
 5. The method according to claim 3,wherein the first metal-containing layer comprises TaN or TaCN and thesecond metal-containing layer comprises Ta or Ti.
 6. The methodaccording to claim 1, wherein the removing comprises removing by sputteretching the first metal-containing layer substantially completely fromthe bottom of the via and from the bottom of the trench, and the methodfurther comprises depositing a second metal-containing layer over thepatterned substrate including onto the sputter etched firstmetal-containing layer.
 7. The method according to claim 1, wherein aminimum total thickness of the conformal Ru layer and the sputter etchedfirst metal-containing layer is between about 1 nm and 10 nm.
 8. Themethod according to claim 4, wherein a minimum total thickness of theconformal Ru layer, the sputter etched first metal-containing layer, andthe second metal-containing layer is between about 1 nm and about 10 nm.9. The method according to claim 1, wherein the Cu alloying metal layercomprises Mg, Mn, Mo, Al, Cr, Ti, Nb, Ca, Be, Zn, Cd, Ag, Pd, or Au, ora combination of two or more thereof.
 10. The method according to claim1, wherein the depositing a Cu alloying metal layer comprises:depositing a layer containing a Cu alloying metal; and depositing a Cumetal layer onto the Cu alloying metal.
 11. The method according toclaim 1, wherein the depositing a Cu alloying metal layer comprises:depositing a layer containing a mixture of a Cu alloying metal and Cumetal onto the conformal Ru layer.
 12. The method according to claim 1,further comprising: annealing the plated Cu layer.
 13. A method ofintegrated substrate processing, comprising: providing a patternedsubstrate containing a via having a sidewall and a bottom and a trenchhaving a sidewall and a bottom; performing an integrated process on thepatterned substrate, the process comprising: depositing a firstmetal-containing layer over the patterned substrate; removing the firstmetal-containing layer substantially completely from the bottom of thevia and at least partially from the bottom of the trench by sputteretching to leave a sputter etched first metal containing layer on aportion of the patterned substrate; depositing a conformal Ru layer overthe first metal-containing layer including onto the sputter etched firstmetal-containing layer; depositing a Cu layer onto the conformal Rulayer; plating Cu over the Cu layer; depositing a Cu alloying metallayer over the plated Cu; and annealing the plated Cu.
 14. The methodaccording to claim 13, wherein the depositing a first metal-containinglayer comprises depositing Ta, TaN, TaC, TaCN, Ti, TiN, W, or WN. 15.The method according to claim 13, further comprising, prior todepositing the conformal Ru layer, depositing a second metal-containinglayer over the patterned substrate.
 16. The method according to claim15, wherein the depositing a second metal-containing layer comprisesdepositing Ta, TaN, TaC, TaCN, Ti, TiN, W, or WN.
 17. The methodaccording to claim 13, wherein the first metal-containing layercomprises TaN or TaCN and the second metal-containing layer comprises Taor Ti.
 18. The method according to claim 13, wherein the removingcomprises removing by sputter etching the first metal-containing layersubstantially completely from the bottom of the via and from the bottomof the trench, and the method further comprises depositing a secondmetal-containing layer over the patterned substrate including onto thesputter etched first metal-containing layer.
 19. The method according toclaim 13, wherein a minimum total thickness of the conformal Ru layerand the sputter etched first metal-containing layer is between about 1nm and 10 nm.
 20. The method according to claim 15, wherein a minimumtotal thickness of the conformal Ru layer, the sputter etched firstmetal-containing layer, and the second metal-containing layer is betweenabout 1 nm and about 10 nm.
 21. The method according to claim 13,wherein the Cu alloying metal layer comprises Mg, Mn, Mo, Al, Cr, Ti,Nb, Ca, Be, Zn, Cd, Ag, Pd, or Au, or a combination of two or morethereof.